Semiconductor light emitting device with thick metal layers

ABSTRACT

A device according to embodiments of the invention includes a semiconductor structure including a light emitting layer sandwiched between an n-type region and a p-type region and first and second metal contacts, wherein the first metal contact is in direct contact with the n-type region and the second metal contact is in direct contact with the p-type region. First and second metal layers are disposed on the first and second metal contacts, respectively. The first and second metal layers are sufficiently thick to mechanically support the semiconductor structure. A portion of a sidewall the device adjacent to one of the first and second metal layers is reflective.

CROSS-REFERENCE TO PRIOR APPLICATIONS

This application is a divisional application of U.S. patent applicationSer. No. 14/360,965, filed on May 28, 2014, which is the U.S. NationalPhase application under 35 U.S.C. §371 of International Application No.PCT/IB2012/056863, filed on Nov. 30, 2012, which claims the benefit ofU.S. Patent Application No. 61/568,281, filed on Dec. 8, 2011. Theseapplications are hereby incorporated by reference herein.

BACKGROUND

1. Field of Invention

The present invention relates to a semiconductor light emitting devicewith thick metal layers.

2. Description of Related Art

Semiconductor light-emitting devices including light emitting diodes(LEDs), resonant cavity light emitting diodes (RCLEDs), vertical cavitylaser diodes such as surface-emitting lasers (VCSELs), and edge emittinglasers are among the most efficient light sources currently available.Materials systems currently of interest in the manufacture ofhigh-brightness light emitting devices capable of operation across thevisible spectrum include Group III-V semiconductors, particularlybinary, ternary, and quaternary alloys of gallium, aluminum, indium, andnitrogen, also referred to as III-nitride materials. Typically,III-nitride light emitting devices are fabricated by epitaxially growinga stack of semiconductor layers of different compositions and dopantconcentrations on a sapphire, silicon carbide, III-nitride, or othersuitable substrate by metal-organic chemical vapor deposition (MOCVD),molecular beam epitaxy (MBE), or other epitaxial techniques. The stackoften includes one or more n-type layers doped with, for example, Si,formed over the substrate, one or more light emitting layers in anactive region formed over the n-type layer or layers, and one or morep-type layers doped with, for example, Mg, formed over the activeregion. Electrical contacts are formed on the n- and p-type regions.

FIG. 1 illustrates an LED including large area metal-to-metalinterconnects, described in more detail in U.S. Pat. No. 7,348,212. Thestructure illustrated in FIG. 1 includes a flip chip light emittingdevice attached to a mount 70. The flip chip device includes a substrate73 attached to semiconductor device layers 74, which include at leastone light emitting or active layer disposed between an n-type region anda p-type region. N-type contact 71 and p-type contact 72 areelectrically connected to the n- and p-type regions of semiconductorstructure 74. Thin metal layers 76 a and 77 a are formed on contacts 71and 72, and thin metal layers 76 b and 77 b are formed on mount 70.Thick ductile metal layers 78 and 79 are plated on either mount 70 orcontacts 71 and 72, thus on either regions 76 a and 77 a or regions 76 band 77 b. Metal layers 78 and 79 are selected to be ductile, have highthermal and electrical conductivity, and be reasonably resistant tooxidation. For example, metal layers 78 and 79 may be Au, which has goodthermal conductivity; Cu, which has even better thermal conductivitythan Au; Ni; or Al, which is less expensive than Au or Cu. Metal layers78 and 79 may be between one and 50 microns thick and are often between5 and 20 microns thick.

SUMMARY

It is an object of the invention to provide a semiconductor deviceincluding thick metal layers that mechanically support the semiconductordevice such that a mount is not required to support the semiconductordevice.

A device according to embodiments of the invention includes asemiconductor structure including a light emitting layer sandwichedbetween an n-type region and a p-type region and first and second metalcontacts, wherein the first metal contact is in direct contact with then-type region and the second metal contact is in direct contact with thep-type region. First and second metal layers are disposed on the firstand second metal contacts, respectively. The first and second metallayers are sufficiently thick to mechanically support the semiconductorstructure. A portion of a sidewall the device adjacent to one of thefirst and second metal layers is reflective.

A method according to embodiments of the invention includes providing awafer of semiconductor devices, the wafer including a semiconductorstructure including a light emitting layer sandwiched between an n-typeregion and a p-type region and first and second metal contacts for eachsemiconductor device, wherein each first metal contact is in directcontact with the n-type region and each second metal contact is indirect contact with the p-type region. First and second metal layers areformed on the first and second metal contacts of each semiconductordevice on the wafer, respectively. The first and second metal layers aresufficiently thick to support the semiconductor structure during laterprocessing. After forming first and second metal layers, an electricallyinsulating layer that fills spaces between the first and second metallayers is formed. The method further includes forming a reflectiveregion disposed adjacent a sidewall of one of the first and second metallayers.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a prior art LED with thick, ductile metalinterconnects.

FIG. 2 illustrates a semiconductor LED suitable for use in embodimentsof the present invention.

FIG. 3 illustrates thick metal layers formed on the metal contacts of asemiconductor LED.

FIG. 4 illustrates the structure of FIG. 3 after planarizing theelectrically insulating layer.

FIG. 5 is a plan view of the structure illustrated in cross sectionalview in FIG. 4.

FIG. 6 illustrates the structure of FIG. 4 after patterning anelectrically insulating layer formed over the thick metal layers.

FIG. 7 illustrates the structure of FIG. 6 after forming bonding pads.

FIG. 8 illustrates thick metal layers and plated redistribution layersformed on the contacts of a semiconductor LED.

FIG. 9 is a plan view of the structure illustrated in cross sectionalview in FIG. 8.

FIG. 10 illustrates the structure of FIG. 8 after forming andplanarizing an electrically insulating layer.

FIG. 11 illustrates the structure of FIG. 10 after forming bonding pads.

FIGS. 12A and 12B are plan views of different implementations of thestructure illustrated in cross sectional view in FIG. 11.

FIG. 13 illustrates a portion of a thick metal layer with a depressionto anchor the electrically insulating material.

FIG. 14 illustrates a portion of a thick metal layer with a protrusionto anchor the electrically insulating material.

FIG. 15 illustrates a portion of a thick metal layer with multiplefeatures to anchor the electrically insulating material.

FIGS. 16, 17, 18, 19, 20, and 21 illustrate forming the protrusionanchoring feature illustrated in FIG. 14.

FIG. 22 illustrates a device with reflective sidewalls.

DETAILED DESCRIPTION

FIG. 2 illustrates a semiconductor light emitting device suitable foruse in embodiments of the invention. Though in the discussion below thesemiconductor light emitting device is a III-nitride LED that emits blueor UV light, semiconductor light emitting devices besides LEDs such aslaser diodes and semiconductor light emitting devices made from othermaterials systems such as other III-V materials, III-phosphide,III-arsenide, II-VI materials, ZnO, or Si-based materials may be used.

The device illustrated in FIG. 2 may be formed by first growing asemiconductor structure on a growth substrate 10, as is known in theart. The growth substrate 10 may be any suitable substrate such as, forexample, sapphire, SiC, Si, GaN, or composite substrates. An n-typeregion 14 may be grown first and may include multiple layers ofdifferent compositions and dopant concentration including, for example,preparation layers such as buffer layers or nucleation layers, and/orlayers designed to facilitate removal of the growth substrate, which maybe n-type or not intentionally doped, and n- or even p-type devicelayers designed for particular optical, material, or electricalproperties desirable for the light emitting region to efficiently emitlight. A light emitting or active region 16 is grown over the n-typeregion. Examples of suitable light emitting regions include a singlethick or thin light emitting layer, or a multiple quantum well lightemitting region including multiple thin or thick light emitting layersseparated by barrier layers. A p-type region 18 may then be grown overthe light emitting region Like the n-type region, the p-type region mayinclude multiple layers of different composition, thickness, and dopantconcentration, including layers that are not intentionally doped, orn-type layers. The total thickness of all the semiconductor material inthe device is less than 10 μm in some embodiments and less than 6 μm insome embodiments.

A p-contact metal 20 is formed on the p-type region. The p-contact metal20 may be reflective and may be a multi-layer stack. For example, thep-contact metal may include a layer for making ohmic contact to thep-type semiconductor material, a reflective metal layer, and a guardmetal layer that prevents or reduces migration of the reflective metal.The semiconductor structure is then patterned by standardphotolithographic operations and etched to remove a portion of theentire thickness of the p-contact metal, a portion of the entirethickness of the p-type region, and a portion of the entire thickness ofthe light emitting region, to form at least one mesa which reveals asurface of the n-type region 14 on which a metal n-contact 22 is formed.

A plan view of the device illustrated in FIG. 2 would look similar tothe plan view illustrated in FIG. 5. N-contact 22 may have the sameshape as thick metal layer 26, described below. P-contact 20 may havethe same shape as thick metal layer 28, described below. The n-contactand the p-contact are electrically isolated by a gap 24 which may befilled with a solid, a dielectric, an electrically insulating material,air, ambient gas, or any other suitable material. The p- and n-contactsmay be any suitable shape and may be arranged in any suitable way.Patterning a semiconductor structure and forming n- and p-contacts iswell known to a person of skill in the art. Accordingly, the shape andarrangement of the n- and p-contacts is not limited to the embodimentillustrated in FIGS. 2 and 5

Also, though a single light emitting device is illustrated in FIG. 2, itis to be understood that the device illustrated in FIG. 2 is formed on awafer that includes many such devices. In the regions 13 betweenindividual devices on a wafer of devices, the semiconductor structuremay be etched down to an insulating layer, which may be an insulatingsemiconductor layer that is part of the semiconductor structure, or thegrowth substrate, as illustrated in FIG. 2.

The LED structure illustrated in FIG. 2, which includes thesemiconductor structure including the n-type region, the p-type region,and the light emitting region, and the n- and p-contacts, is representedin simplified form by structure 12 in the following figures.

In embodiments of the invention, thick metal layers are formed on the n-and p-contacts of the LED. The thick metal layers may be formed on awafer scale, before a wafer of devices is diced into individual orsmaller groups of devices. The thick metal layers may support the devicestructure of FIG. 2 after the wafer of devices is diced, and may supportthe device structure of FIG. 2 during removal of the growth substrate insome embodiments.

FIG. 3 illustrates thick metal layers formed on the n- and p-contacts ofLED 12. In some embodiments, a base layer, which is not shown in FIG. 3,is formed first. The base layer is a metal layer or layers on which thethick metal layers are deposited. For example, the base layer mayinclude an adhesion layer, the material of which is selected for goodadhesion to the n- and p-contacts, and a seed layer, the material ofwhich is selected for good adhesion to the thick metal layers. Examplesof suitable materials for the adhesion layer include but are not limitedto Ti, W, and alloys such as TiW. Examples of suitable materials for theseed layer include but are not limited to Cu. The base layer or layersmay be formed by any suitable technique including, for example,sputtering or evaporation.

The base layer or layers may be patterned by standard lithographictechniques such that the base layer is present only where the thickmetal layers are to be formed. Alternatively, a photoresist layer may beformed over the base layer and patterned by standard lithographictechniques to form openings where the thick metal layers are to beformed.

Thick metal layers 26 and 28 are formed simultaneously over the n- andp-contacts of LED 12. Thick metal layers 26 and 28 may be any suitablemetal such as, for example, copper, nickel, gold, palladium,nickel-copper alloy, or other alloys. Thick metal layers 26 and 28 maybe formed by any suitable technique including, for example, plating.Thick metal layers 28 and 30 may be between 20 μm and 500 μm in someembodiments, between 30 μm and 200 μm in some embodiments, and between50 μm and 100 μm in some embodiments. Thick metal layers 26 and 28support the semiconductor structure during later processing steps, inparticular removal of the growth substrate, and provide a thermalpathway to conduct heat away from the semiconductor structure, which mayimprove the efficiency of the device.

After thick metal layers 26 and 28 are formed, an electricallyinsulating material 32 is formed over the wafer. The electricallyinsulating material 32 fills gaps 30 between the thick metal layers 26and 28 and also fills gaps 34 between LEDs 12. The electricallyinsulating material 32 may optionally be disposed over the tops of thickmetal layers 26 and 28. Electrically insulating material 32 is selectedto electrically isolate metal layers 26 and 28 and to have a coefficientof thermal expansion that is matched or is relatively close to that ofthe metal(s) in thick metal layers 26 and 28. For example, electricallyinsulating material 32 may be epoxy or silicone in some embodiments.Electrically insulating material 32 may be formed by any suitabletechnique, including, for example, overmolding, injection molding,spinning on, and spraying on. Overmolding is performed as follows: Anappropriately sized and shaped mold is provided. The mold is filled witha liquid material, such as silicone or epoxy, which when cured forms ahardened electrically insulating material. The mold and the LED waferare brought together. The mold is then heated to cure (harden) theelectrically insulating material. The mold and the LED wafer are thenseparated, leaving the electrically insulating material 32 over theLEDs, between the LEDs, and filling any gaps on each LED. In someembodiments, one or more fillers are added to the molding compound toform composite materials with optimized physical and materialproperties.

FIG. 4 illustrates an optional processing step, where the device isplanarized, for example by removing any electrically insulating materialoverlying thick metal layers 26 and 28. Electrically insulating material32 may be removed by any suitable technique, including, for example,microbead blasting, fly cutting, cutting with a blade, grinding,polishing, or chemical mechanical polishing. The electrically insulatingmaterial 30 between thick metal layers 26 and 28 is not removed, and theelectrically insulating material 34 between adjacent LEDs is notremoved.

FIG. 5 is a plan view of the structure shown in cross sectional view inFIG. 4. The cross section shown in FIG. 4 is taken at the axis shown inFIG. 5. The thick metal layer 26 formed on the n-contact illustrated inFIG. 2 is circular, though it may have any shape. The thick metal layer26 is surrounded by the thick metal layer 28 formed on the p-contactillustrated in FIG. 2. Thick metal layers 26 and 28 are electricallyisolated by electrically insulating material 30, which surrounds thickmetal layer 26. Electrically insulating material 34 surrounds thedevice.

The shape and placement of the metal layers electrically connected tothe n- and p-type regions may be altered (i.e. thick metal layers 26 and28 may be redistributed) by forming additional layers of insulatingmaterial and metals, as illustrated in FIGS. 6 and 7. In FIG. 6 anelectrically insulating layer 36 is formed then patterned by standardlithographic techniques to form an opening 38 aligned with thick metallayer 26 and an opening 40 aligned with thick metal layer 28.Electrically insulating layer 36 may be any suitable material includingbut not limited to a dielectric layer, a polymer, benzocyclobutene,oxide of silicon, nitride of silicon, silicone, and epoxy. Electricallyinsulating layer 36 may be formed by any suitable technique includingbut not limited to plasma enhanced CVD, spinning on, spraying on, andmolding.

In FIG. 7, metal bonding pads 42 and 44 are formed on thick metal layers26 and 28, respectively, in openings 38 and 40, respectively. In someembodiments, metal bonding pads 42 and 44 are suitable for connection toa structure such as a PC board, for example by reflow-soldering. Bondingpads 42 and 44 may be, for example, nickel, gold, aluminum, alloys,stacks of metals, or solder. Bonding pads 42 and 44 may be formed by anysuitable technique, including, for example, plating, sputtering,evaporation, or screen printing. Bonding pad 42 is electricallyconnected to n-type region 14 of FIG. 1. Bonding pad 44 is electricallyconnected to p-type region 18 of FIG. 1.

An alternative process for forming a device with thick metal layers andbonding pads is illustrated beginning in FIG. 8. In FIG. 8, thick metallayers 26 and 28 are formed, as described above in reference to FIG. 3.Redistribution layers 46 and 48 are then formed on thick metal layers 26and 28, respectively. Redistribution layers 46 and 48 are smaller thanthick metal layers 26 and 28. For example, redistribution layers 46 and48 may be formed by first forming a photoresist layer over thick metallayers 26 and 28, then patterning the photoresist layer such thatopenings in the photoresist layer are disposed where redistributionlayers 46 and 48 are to be formed. Redistribution layers 46 and 48 arethen formed by any suitable technique. For example, redistributionlayers 46 and 48 may be copper, formed by plating.

FIG. 9 is an example of a plan view of the structure shown in crosssectional view in FIG. 8. Redistribution layer 46 is formed on thickmetal layer 26, which is surrounded by thick metal layer 28. Gap 24electrically isolates thick metal layers 26 and 28. Redistribution layer48 is formed on thick metal layer 28 but has a smaller lateral extentthan thick metal layer 28.

In FIG. 10, an electrically insulating material 50 is formed over thestructure illustrated in FIG. 8, as described above in reference to FIG.3. The electrically insulating material is then planarized, as describedabove in reference to FIG. 4. Electrically insulating material 50 fillsthe gaps 51 between thick metal layers 26 and 28, the gap 52 betweenredistribution layers 46 and 48, and the gaps 54 between neighboringLEDs.

In FIG. 11, bonding pads 56 and 58 are formed over redistribution layers46 and 48, respectively. Bonding pads 56 and 58 may be the same as thebonding pads described above in reference to FIG. 7. FIGS. 12A and 12Bshow examples of plan views of the structure shown in cross sectionalview in FIG. 11. In the embodiment illustrated in FIG. 12A, bonding pad56, which is electrically connected to redistribution layer 46, has amuch larger lateral extent than redistribution layer 46 and thick metallayer 26. Bonding pad 58, which is electrically connected toredistribution layer 48, has a similar lateral extent as redistributionlayer 48. In the embodiment illustrated in FIG. 12B, bonding pad 56 issubstantially the same size and shape as bonding pad 58. A gap 57electrically isolates bonding pads 56 and 58.

In some embodiments, the growth substrate 10 is removed from thestructure illustrated in FIG. 7 or the structure illustrated in FIG. 11.The growth substrate may be removed by any suitable technique,including, for example, laser lift-off, etching, mechanical techniquessuch as grinding, or a combination of techniques. In some embodiments,the growth substrate is sapphire and is removed by wafer-scale laserlift-off. Since the sapphire substrate does not need to be thinnedbefore removal and has not been diced, it can be reused as a growthsubstrate. The surface of the semiconductor structure exposed byremoving the growth substrate, typically a surface of n-type region 14,may be optionally thinned and roughened, for example byphotoelectrochemical etching. In some embodiments, all or part of thegrowth substrate remains part of the final device structure.

The wafer of devices is then diced into individual or groups of LEDs.Individual or groups of LEDs may be separated by sawing, scribing,breaking, cutting, or otherwise separating the electrically insulatingmaterial 34 or 54 between neighboring LEDs.

As illustrated in FIGS. 7 and 11, the electrically insulating material34, 54 between neighboring LEDs may be narrow relative to its height,which may cause the electrically insulating material to pull away fromthe sides of LED 12 and thick metal layer 26 or 28 during dicing. If theelectrically insulating material 34, 54 pulls away from LED 12, the lackof support can cause LED 12 to crack, which can lead to poor deviceperformance or even device failure.

In some embodiments, three-dimensional anchoring features are formed onthe side of the thick metal layer in contact with the electricallyinsulating material 34, 54 at the edge of LED 12, in order to anchor theelectrically insulating material 34, 54 in place. The three-dimensionalanchoring features interrupt the smooth, flat sidewall of the thickmetal layer. Examples of anchoring features are illustrated in FIGS. 13,14, and 15. Though FIGS. 13, 14, and 15 show the anchoring featuresformed on the sidewall of thick metal layer 28, which is electricallyconnected to p-type region 18, anchoring features may be formed oneither thick metal layer 26 or thick metal layer 28, or both. Also,alternatively or in addition to forming anchoring features on a sidewallfacing the edge of a device, anchoring features may be formed on thesidewall of a thick metal layer that is in the interior of the LED (forexample, on the sidewall of thick metal layer 26 or 28 that is incontact with electrically insulating material 51, as illustrated in FIG.11).

In the structure illustrated in FIG. 13, the anchoring feature is adepression 60 formed in the otherwise flat sidewall of thick metal layer28. Depression 60 fills with electrically insulating material 34, 54 toanchor the electrically insulating material.

In the structure illustrated in FIG. 14, the anchoring feature is aprotrusion 62 protruding from the otherwise flat sidewall of thick metallayer 28.

In the structure illustrated in FIG. 15, the anchoring feature is aseries of depressions and/or protrusions 64.

Depression 60 or protrusion 62 may be formed by a series of metalforming, electrically insulating material forming, planarizing, andpatterning steps as illustrated in FIGS. 16, 17, 18, 19, 20, and 21.Only a portion of a thick metal layer 28 is illustrated. A thick metallayer 26 with anchoring features could also be formed as illustrated.The process described in FIGS. 16, 17, 18, 19, 20, and 21 can be usedwith either the process illustrated in FIGS. 3, 4, 6, and 7 or theprocess illustrated in FIGS. 8, 10, and 11. Though in the descriptionbelow, the metal layer portions are formed by plating and theelectrically insulating material portions are formed by molding, anysuitable metal deposition or insulating material deposition techniquecan be used.

In FIG. 16, a first portion 28A of the thick metal layer is plated overLED 12, as described above. In FIG. 17, a first portion 34A ofelectrically insulating material 34 or 54 is molded over first metalportion 28A, then planarized, as described above. A photoresist layer isthen formed and patterned to form openings where second portion 28B ofthick metal layer 28 is to be formed. In FIG. 18, second metal portion28B is plated on first metal portion 28A. As shown in FIG. 18, secondmetal portion 28B has a larger lateral extent than first metal portion28A. In FIG. 19, a second portion 34B of electrically insulatingmaterial 34 or 54 is molded over second metal portion 28B, thenplanarized. A photoresist layer is then formed and patterned to formopenings where third portion 28C of thick metal layer 28 is to beformed. In FIG. 20, third metal portion 28C is plated on second metalportion 28B. As shown in FIG. 20, third metal portion 28C has a smallerlateral extent than second metal portion 28B. The portion of secondmetal portion 28B that extends beyond first metal portion 28A and thirdmetal portion 28C forms protrusion 62, which anchors electricallyinsulating material 34A, 34B, and 34C. It will be clear to a person ofskill in the art that the processing steps illustrated in FIGS. 16, 17,18, 19, 20, and 21 can be modified and/or repeated to form any of thestructures illustrated in FIGS. 13, 14, and 15.

In the structures described above, the sides of the device, i.e. thesides of electrically insulating material 34 in FIGS. 7 and 54 in FIG.11, may be absorbing to light. Particularly in applications that makeuse of mixing chambers, it is important that all surfaces be asreflective as possible. In some embodiments, a reflective material isadded to insulating material 34, 54, such that after dicing, the sidesof electrically insulating material 34, 54 are reflective. For example,highly reflective TiO₂ and/or calcium silicate particles may be mixedwith the electrically insulating material, which may be epoxy orsilicone, for example, that is molded or otherwise disposed over thewafer, as described above for example in reference to FIG. 3.

In some embodiments, in addition to or instead of reflective material,thermally conductive material may be added to insulating material 34,54. For example, particles of aluminum nitride, SiO₂, graphite, BN, orany other suitable material can be added to insulating material 34, 54to improve the thermal conductivity of the structure and/or to engineerthe coefficient of thermal expansion (CTE) of the insulating material tomore closely match the CTE of the semiconductor structure, the thickmetal layers, or both.

In some embodiments, as illustrated in FIG. 22, the device is diced suchthat the edges of the device are the sidewalls of thick metal layer 28,rather than electrically insulating material 34, 54. In someembodiments, after dicing, the sidewalls of thick metal layer 28treated, for example by wet chemical etching, to reduce surfaceroughness. Reducing the surface roughness may increase the reflectivityof the sidewalls. In some embodiments, after dicing, while the device isstill attached to the handling foil used for dicing, a reflective metalcoating 66 such as an Al, Ni, Cr, Pd, or Ag coating, a reflective alloy,or a stack of reflective coatings, is formed on the sides of thick metallayer 28, for example by physical vapor deposition or electrolessplating.

In some embodiments, the side coating 66 is an insulating reflectivematerial that is placed over the sidewalls of the device after thedevice is diced, while the device is still attached to the handling foilfor dicing. For example, individual devices may be separated and whilethe individual devices are on the handling foil, the separation lanesmay be filled with a highly reflective material. The highly reflectivematerial may then be separated again. The wafer of devices can be formedwith separation lanes wide enough to accommodate two separation steps,or the handling foil can be stretched twice to accommodate twoseparation steps. Examples of suitable reflective materials includesilicone, or a transparent material such as silicone or epoxy filledwith reflective particles such as TiO₂ particles.

One or more optional structures such as filters, lenses, dichroicmaterials, or wavelength converting materials may be formed over theLEDs, before or after dicing. A wavelength converting material may beformed such that all or only a portion of the light emitted by the lightemitting device and incident on the wavelength converting material maybe converted by the wavelength converting material. Unconverted lightemitted by the light emitting device may be part of the final spectrumof light, though it need not be. Examples of common combinations includea blue-emitting LED combined with a yellow-emitting wavelengthconverting material, a blue-emitting LED combined with green- andred-emitting wavelength converting materials, a UV-emitting LED combinedwith blue- and yellow-emitting wavelength converting material, and aUV-emitting LED combined with blue-, green-, and red-emitting wavelengthconverting materials. Wavelength converting materials emitting othercolors of light may be added to tailor the spectrum of light emittedfrom the device. The wavelength converting material may be conventionalphosphor particles, quantum dots, organic semiconductors, II-VI or III-Vsemiconductors, II-VI or III-V semiconductor quantum dots ornanocrystals, dyes, polymers, or materials such as GaN that luminesce.Any suitable phosphor may be used, including but not limited togarnet-based phosphors such as Y₃Al₅O₁₂:Ce (YAG), Lu₃Al₅O₁₂:Ce (LuAG),Y₃Al_(5-x)Ga_(x)O₁₂:Ce (YAlGaG), (Ba_(1-x)Sr_(x))SiO₃:Eu (BOSE), andnitride-based phosphors such as (Ca,Sr)AlSiN₃:Eu and(Ca,Sr,Ba)₂Si₅N₈:Eu.

The thick metal layers 26 and 28 and the electrically insulatingmaterial that fills gaps between the thick metal layers and betweenneighboring LEDs provide mechanical support to the semiconductorstructure, such that an additional mount such as a silicon or ceramicmount is not required. Eliminating the mount may reduce the cost of thedevice and may simplify the processing required to form the device.

Having described the invention in detail, those skilled in the art willappreciate that, given the present disclosure, modifications may be madeto the invention without departing from the spirit of the inventiveconcept described herein. Therefore, it is not intended that the scopeof the invention be limited to the specific embodiments illustrated anddescribed.

What is being claimed is:
 1. A method comprising: providing a wafer ofsemiconductor devices, the wafer comprising: a semiconductor structurecomprising a light emitting layer sandwiched between an n-type regionand a p-type region; and first and second metal contacts for eachsemiconductor device, wherein each first metal contact is in directcontact with the n-type region and each second metal contact is indirect contact with the p-type region; forming first and second metallayers on the first and second metal contacts of each semiconductordevice on the wafer, respectively, wherein the first and second metallayers are sufficiently thick to support the semiconductor structureduring later processing; after forming first and second metal layers,forming an electrically insulating layer that fills spaces between thefirst and second metal layers; and forming a reflective region disposedadjacent a sidewall of one of the first and second metal layers.
 2. Themethod of claim 1 wherein forming first and second metal layerscomprises plating first and second metal layers on the wafer.
 3. Themethod of claim 1 wherein forming a reflective region comprises formingthe electrically insulating layer with reflective material.
 4. Themethod of claim 3 wherein the reflective material comprises TiO₂ mixedwith one of silicone and epoxy.
 5. The method of claim 1 wherein forminga reflective region comprises forming a reflective metal on a sidewallof one of the first and second metal layers.
 6. The method of claim 5further comprising: attaching the wafer to handling foil; and dicing thewafer into individual or groups of semiconductor devices while attachedto the handling foil; wherein forming a reflective metal on a sidewallof one of the first and second metal layers comprises depositing thereflective metal after dicing the wafer, while the wafer is stillattached to the handling foil.
 7. The method of claim 1 furthercomprising: attaching the wafer to handling foil; and dicing the waferinto individual or groups of semiconductor devices while attached to thehandling foil; wherein forming a reflective region disposed adjacent asidewall of one of the first and second metal layers comprises disposingan electrically insulating reflective sheet adjacent to the sidewall ina region formed by dicing the wafer, while the wafer is still attachedto the handling foil.